A semiconductor manufacturing process is generally considered to be highly self-consistent, that is, the manufacturing process is very good at producing “exact” copies of an integrated circuit design. This is especially the case for semiconductor products operated in the digital domain, for example, microprocessors and/or graphical processing units (GPUs). Functionally, the semiconductor arts have succeeded in generally producing many copies that function similarly.
Unfortunately, numerous analog characteristics of an integrated circuit are highly variable, which can lead to varied analog function/performance from circuit to circuit and/or chip to chip. For example, threshold voltage, capacitance, gate delay, current consumption, minimum operating voltage and maximum operating frequency may vary 30% or more from chip to chip of the same design utilizing nominally the same manufacturing process. In addition, once manufactured, such characteristics also vary greatly according to operating voltage and temperature. For example, an integrated circuit is generally capable of a higher operating frequency at a higher voltage and lower temperature, in comparison to operation at a lower voltage and higher temperature.
A clock signal is an oscillating electronic signal. Many complex integrated circuits, for example, microprocessors and/or graphical processing units, utilize a synchronizing signal generally known as or referred to as a clock or clock signal. Such a clock signal may be used to control and/or synchronize many aspects of an integrated circuit's operation, for example, especially that of synchronous digital circuits. The frequency of this signal is related to the performance of the integrated circuit, and is frequently utilized in advertizing and as a means of comparison among similar competitive offerings, e.g., “this chip operates at 2.4 GHz.”
Under the conventional art, due to the variability of the integrated circuit's operation due to manufacturing variability and operating conditions, a maximum clock frequency is typically specified by a manufacturer after qualification testing of a population of integrated circuits. A maximum clock frequency is determined to ensure reliable operation of the integrated circuit across a specified operating environment, e.g., a range of operating voltage and operating temperature, sometimes known as or referred to as an operating window or operating envelope. Once such a maximum clock frequency has been determined, a highly stable clock signal, e.g., of the maximum or lower frequency, typically derived from a crystal source, is provided to the integrated circuit for operation.
Unfortunately, since the maximum operating frequency has been determined to be satisfactory under all process variations and operating conditions, including, for example, the worst case combination of such process and operating variations, the maximum operating frequency available under the conventional art is generally less than any given integrated circuit can achieve at its actual operating conditions. Such less than optimal operation results in undesirable performance degradation of the integrated circuit, and a diminished competitive positioning of the integrated circuit.